P2pWeb Slide1Peer-To-Peer : Concept, Tools and Applications The p2pweb Project Low cost Peer to Peer...

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Slide1Peer-To-Peer : Concept, Tools and Applications

The p2pweb Project

Low cost Peer to Peer solutions for high availability web hosting

19 Mai 2005

Séminaire

« Peer-To-Peer : Concept, Tools and Applications »

Ecole d’ingénieurs de Genève

p2pWeb


Agenda

1. The Project goals

2. Web hosting solutions and architecture

3. The p2pweb solution

4. Project constraints and key technologies5. Related projects

6. The project components– Global server load balancing system– Distributed set of web server– Monitoring system– Node architecture and hardware

7. Conclusion

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To explore and implement low cost solutions for high availability web hosting

“Do More with Less”

Our targets are :• small or medium structures (associations, NGO, etc …)• with limited resources (money, IT people)• with important web hosting needs (bandwidth available)

– rich and complex web site– medium to high web traffic– high availability and visibility needs

It may fit very well the needs of many project in Least Developed Countries : TeleCentres Networks, Rural Organisations, Universities, Cultural Centres, Public

Libraries, Community Multimedia Centres, Health Networks, etc ...

The Project goals

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Afromix.org (personal web site)A portal of African and Caribbean Cultures since 1993

A complex web site using multiple technologies

• in house Perl Content Management System (CMS)

• an extended discographic database (1600 artist, more than 50 styles from all Africa and French West Indies)

• multilingual (French, English, Spanish) site running on a JAVA application server (Tomcat)

• about 25 000 files, 400 000 pages/month, 2 million hits/month, 60 000 unique visitors/month

Mediaport.net (community web site)One of the first French web pioneer, first developed in INA

• mostly static content (near 10 000 files)

• multilingual (French, English) site running on a PHP CMS (ezpublish)

• it’s the main p2pweb test platform and it will evolve to an open web hosting solution for artistic and cultural web projects (an editorial committee is forming)

Example of hosted web site

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The web hosting market

• Free web hosting– Very limited

• static html or small PHP site (limited computing resources)

• can’t use your own domain name

• Professional web hosting– A broad range of services

• private virtual server

• dedicated server

• Co/location

– But price is quite high• 100-200€/month for one dedicated server

• and maintenance can be complex

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Centralized architecture

Server in one location :

Server and Internet link are single point of failure (SPOF)

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Centralized architecture (cont.)

Database cluster

SAN Storage

Application Servers

Load Balancers

Web servers

Reverse Proxy / Cache / SSL accelerators

Load Balancers

Multi-homing with BGP routing

High availability architecture

Datacenter hosting

- BGP routing

- hardware load balancing

- SAN storage

In theory, no SPOF

•but very complex architecture

•very high cost

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CDN Architecture

Content Delivery Network

Service delivered by companies like Akamai, Speedera, and others.

Edge servers provide caching and data replication for fast delivery to clients worldwide.

A solution for very high traffic web site.

Very expensive solution.

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alternative web hosting

• Community based web hosting– Initiatives from various associations

ouvaton.coop, globenet.net, autre.net, altern.net, ...

– Most of the time, people share their money and knowledge to buy and administer one or two dedicated server.

• Home server– We now have sufficient bandwidth (ADSL) computing power

(PCs), good software (apache, linux …)

– We lack reliability !

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First idea : big home server

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Second idea (better one)

Lots of people (family, friends, co-workers, …) already have :

• An ADSL Internet access or Permanent High Speed Connection

• One or more PCs (with a lot of unused disk space)

So, what about sharing those resources to build a more powerful and resilient network of web servers

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Web Hosting : the p2pweb way

ADSL ISP 1

ADSL ISP 2

ADSL ISP 3

Each member of the p2pweb network share a portion of his Internet bandwidth (most of the time an ADSL line) and host a small server.

The result is a powerful network that is the sum of the bandwidth and computing resources of all the members.

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A peer to peer solution

• Somehow, it’s a return to the very fundamentals principles of Internet:– a cooperative solution (network of servers)– a distributed solution (no central control)– a fault tolerant solution (resilience)

• But with all the power of existing internet and open source technologies– consumer computers and internet access– overlay network and services over the Internet– It is a peer to peer solution !

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The project constraints

• Unreliable component– Node failure is not an exception, it’s the rule.– Internet link failure, power outage, server crash …

• Automatic function– Murphy’s law : servers will always crash when there

is nobody to fix the problem (at night, when you are on vacation …)

• Pragmatic approach – Build from existing component – Simple and efficient solutions are priority choices

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Key technologies

Mass market products are available at low cost now !

• ADSL lines– 1 Mb/s Up - 15Mb/s Down for 30€ / month (free.fr)

• ADSL router / firewall / ethernet or wifi– D-LINK, NetGear, LINKSYS from 75 to 150 €

• Small Servers– PC barebones (Asus, Biostar, Shuttle …)

• from 300 to 500 € – mini iMac (Apple)

• 499 €• Open Source Software

– BSD, Linux, apache, tomcat, etc …

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Related projects

YouServ (IBM) http://www.almaden.ibm.com/cs/people/bayardo/userv/

• YouServ is software that forms a webserving "grid" by allowing its users to pool their desktop computing resources to create one large, virtual web-space.

• An intranet project, more oriented on desktop file sharing.

• Unfortunately not open source

Vergenet (Simon Horman) http://www.vergenet.net/

• Vergenet has servers located in Sydney, Amsterdam, London, Tokyo and Indiana. These servers are all running Linux and a variant of Super Sparrow to load balance traffic between them.

• Super Sparrow enables users to load balance traffic between geographically separated points of presence by finding the site network-wise closest to clients. This is done by accessing BGP routing information (but it require direct access to a BGP router)

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Related projects (cont.)

Coral (New York University) http://www.coralcdn.org/

• Coral is peer-to-peer content distribution network, comprised of a world-wide network of web proxies and name servers

• Publishing through Coral is as simple as appending a short string to the hostname of objects' URLs; a peer-to-peer DNS layer transparently redirects browsers to participating caching proxies

• an URL like www.myserver.com/some/path.html becomes www.myserver.com.nyud.net:8090/some/path.html

• Coral is in fact running on top of the planet-lab network (a grid computing research network : http://www.planet-lab.org/)

Globule (Vrije University Amsterdam) http://www.globule.org/

• Globule is a module for the Apache Web server that allows a given server to replicate its documents to other Globule servers. Clients are automatically redirected to one of the available replicas.

• The project provide both content replication and HTTP or DNS based redirection mechanisms

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P2PWeb - Project Components

• A global server load balancing system– Two main functions

• Load balance the traffic on the web servers• Provide failover = only send traffic on alive web servers

• A distributed set of web server– And a set of tools to :

• Publish content on the servers• Keep all servers in sync (replication mechanism)

• Monitoring services

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Global server load balancing

• Load balancing– achieved using Round Robin DNS

• simple system, with well known limits (http://www.tenereillo.com/GSLBPageOfShame.htm)

• Failover– achieved by coupling a monitoring system (NAGIOS) with the

DNS• DNS entries have short TTL (time to live)• NAGIOS monitors each web servers• When a server change state (for example DOWN) a special handler is

called that update the DNS entry and reload the DNS• The failed server is no longer announced by the DNS

To have a fully redundant system, we use 3 independents DNS (all primary), each running its own NAGIOS instance

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GSLB : Failover illustrated

Initial DNS entries : all server are upwww 300 IN A 82.66.103.28www 300 IN A 195.101.152.113www 300 IN A 82.232.203.167www 300 IN A 66.35.250.210

Server 195.101.152.113 failsIn the syslog trace, we can see :22:22:46 nagios: SERVICE ALERT: ns1;HTTP-P2PWEB;CRITICAL;SOFT;1;Connection refused by host 22:23:47 nagios: SERVICE ALERT: ns1;HTTP-P2PWEB;CRITICAL;SOFT;2;Connection refused by host 22:24:46 nagios: SERVICE ALERT: ns1;HTTP-P2PWEB;CRITICAL;HARD;3;Connection refused by host

After 3 unsuccessfull try, a notification is send by email to the admin22:24:46 nagios: SERVICE NOTIFICATION: nagios;ns1;HTTP-P2PWEB;CRITICAL;notify-by-email;Connection refused by host

The specific handler is called22:24:47 nagios: SERVICE EVENT HANDLER: ns1;HTTP-P2PWEB;CRITICAL;HARD;3;http_p2pweb_handler

And the DNS is reloaded22:24:47 named[17379]: master/p2pweb.net.zone:1: no TTL specified; using SOA MINTTL instead

And now we can verify that the DNS entries arewww 300 IN A 82.66.103.28;www 300 IN A 195.101.152.113www 300 IN A 82.232.203.167www 300 IN A 66.35.250.210

Failover time is : 2 or 3 minutes (NAGIOS) + DNS max TTL (here 5 minutes) = less than 10 minutes

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GSLB : next steps

Improvements :– Better service provisioning (manual process for now)– Better support for “long downtime”

• When a server crash for a long period of time and then recovers its content may be outdated

• We must not announce it back until it has re-synchronize itself

– Proximity load balancing• The goal is to load balance traffic between geographically distributed servers by

finding the site network-wise closest to clients.

• A technology used in the CDN (Content Delivery Network) world

We can use part of the globule project, as Globule support DNS redirection based on 'AS-path length' policy (used in BGP routing) which tries to redirect clients to a server close to them.

These BGP information's can be collected through routeviews.org (no direct access to a BGP router needed)

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Web server content management

We have a set of web servers and we need tools to :– Publish content on all servers– Keep them in sync (content replication)

Two main replication strategies• primary backup : one master server to form replicas• active replication : if any changes, one replica propagates them back to all the other ones

ADSL ISP 1

ADSL ISP 2

ADSL ISP 3

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static content replication

One server play the master’s role– Content is published first on the master (for example via FTP)– Then the content is either pushed or pulled on the replica

The easiest way is to use rsync (rsync.samba.org)Content can be pulled via anonymous rsync from masterContent can be pushed via rsync over ssh (using private/public key pair for

security)

ADSL ISP 1

ADSL ISP 2

ADSL ISP 3

Master

Replica

Replica

Replica

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Content replication : rsync

rsync is a file transfer program for Unix systems. rsync provides a very fast method for bringing remote files into sync. It does this by sending just the differences in the files across the link, without requiring that both sets of files are present at one of the ends of the link beforehand.

Anonymous rsync server (pull mode)• Run as a standalone daemon or can be launched by inetd• Advanced security options (read-only, chroot, IP access list)• Use : run from crontab on each mirror

rsync -a master.mydomain.com::www/ /data/www/

Rsync over SSH (push mode)• Need ssh access on each mirror• And ssh cryptographic keys exchange for unattended operation• Use : run on demand or from crontab on master

rsync -a /data/www/ [email protected]::/data/www/

Useful options--compress compress file data during the transfer--bwlimit=KBPS limit I/O bandwidth; KBytes per second

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Content distribution : Satellite

For a lot of geographically distributed mirrors, an interesting solution can be Datacasting over satellite

• Technology used by some CDN vendors– Skycache, cidera, Skystream.com, panamsat.com

• Now available at lower cost from worldspace.fr (SatPost Solution)

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Use of CMS

Nowadays most webmasters use CMS (Content Management System) tools for publishing

– A lot of open source and commercial tools• Spip, mambo, typo3, phpnuke, … (php)

• Bricolage, metadot, slashcode, … (perl)

• Cofax, opencms, magnolia, jahia, … (java)

• Plone, cps, zwook, … (python)

• But none of them has direct support for a distributed architecture

• Most use a database as a backstore

• Database distributed transaction and replication is a hard problem

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CMS : a pragmatic solution

The webmaster publish using the CMS as usual– The content is exported as static html files– Then distributed on the replicas using rsync

Constraint : the CMS must support export with “static like URLs”Either directly or thru URL rewriting/article/sport/2005/4/13/football.html (good)/article.php?id_category=3&id_article=25 (bad for mirroring)

ADSL ISP 1

ADSL ISP 2

ADSL ISP 3

webmaster

Master : static html files

Replica

CMS

Back officehtml export

Replica

Replica

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CMS : distributed architecture (1)

Example : a non-governmental organization has activity over 4 countries and want to provide a global web presence. The same global web design and tools are used on all servers.

Local publishingEach local webmaster publish news about his country using the CMS on the local server

Content exchange using web servicesEach local web server “collect” (pull) new articles from the other servers using some RSS (Really Simple Syndication) web services

Global web presenceGlobal content is (re)constructed on each server (from all data from the others) and served on Internet

Such solution may be constructed by hacking/customizing existing CMS

ADSL ISP 1

ADSL ISP 2

ADSL ISP 3

Ivory coast

Senegal

Burkina faso

Mali

XML content exchange

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CMS : distributed architecture (2)

CMS + Message-oriented middleware (MOM)

A MOM is a client/server infrastructure that increases the interoperability, portability and flexibility of an application by allowing the application to be distributed over multiple heterogeneous platforms.

Thru the use of queue system, a MOM can provide asynchronous reliable data exchange.

MOM is typically asynchronous and peer-to-peer and supports– Point to point communication– Publish and subscribe communication

There is a standardized interface in Java : JMS (java Message Service) APIVarious open source implementation in the java world

ActiveMQ (activemq.codehaus.org)OpenJMS (openjms.sourceforge.net)Joram (joram.objectweb.org)MantaRay (mantamq.org)

No CMS use it now (as far as i know), but it may be a very good solution

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Performance monitoring

We collaborate with the webperf.org project– WebPerf is a system for measuring response time of specified URLs

from multiple locations on the internet.– The project is founded on the premise that there are lot of other

companies who also require such a monitoring service. If the other companies are willing to monitor our URLs, we will montior theirs (a free co-peering arrangement).

Some perl script installed on local node collect data from other web site, then data are pushed to a central repository for further analysis.

A web interface allow members to display various statistics.

A view of one’s web site as seen from all other the world.

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Webperf.org : sample graph (1)

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Node architecture and security

ADSL or Cable modem

Ethernet router/firewallOptional Wifi access point

Private Ethernet LAN

Ethernet link

Internet

Security

Mandatory

•Hardware router/firewall with NAT capabilities

•Internal private network using RFC 1918 IP address (192.168.x.y)

No incoming traffic from the outside other than required

Controlled via redirect on the firewall•http (port 80)

•ssh (port 22, optional)

Web server

P2pweb traffic

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Node hardware (example)

Run on the corner of a desk

•An ethernet and wifi switchConnect other computers (not shown here)

•A web and application serverMac mini (apple) running apache2 and tomcat

•A firewallEmbedded PC (www.pcengines.ch) running pf (packet filter) on OpenBSD from a compact flash

No noise, and low electric power consumption (near 50W)

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Conclusion

• It can be done (at low cost)

• It runs, with good results(service uptime measured by siteuptime.com)

www.p2pweb.nethosted by the p2pweb networkmonitored Since: 9/23/2004Outages: 40Total Uptime: 99.560%Downtime/year: 38,5 hours

www.afromix.orghosted on a single node monitored Since: 9/23/2004Outages: 37Total Uptime: 97.634%Downtime/year: 207,3 hours

• Still a lot of improvementsNot already an easy to use solution : node admin still require good Unix knowledge

• Most important : a new way to design web applications

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The Future

What we can provide right nowP2pweb.net : a global load balancing solution for any distributed web project

• Just provide the servers IP addresses and a health check URL

Mediaport.net : a Community web hosting solution

• We can host various web projects

We are looking for Partnerships in the following domains :Packaging an easy and ready to use solution for deploying web mirrors

(industrializing the solution)

• dedicated LINUX or BSD Distro with preinstalled packages

• “all in one” solution : Java CMS + MOM in one webapp application

Helping in deploying such solution in Least Developed Countries

The P2PWeb Solution fits perfectly for Least Developed Countries with weak bandwidth and low connectivity,

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Contacts

P2pweb is a SourceForge project (bsd license)www.p2pweb.net or mediaport.sourceforge.net

Contacts :about the project :

[email protected]

you want to be hosted on mediaport.net :[email protected]

[email protected]

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Questions

Thank you

• Questions ?

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